/*
 *  Copyright 2018 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

package org.webrtc;

/**
 * The TimestampAligner class helps translating camera timestamps into the same timescale as is
 * used by rtc::TimeNanos(). Some cameras have built in timestamping which is more accurate than
 * reading the system clock, but using a different epoch and unknown clock drift. Frame timestamps
 * in webrtc should use rtc::TimeNanos (system monotonic time), and this class provides a filter
 * which lets us use the rtc::TimeNanos timescale, and at the same time take advantage of higher
 * accuracy of the camera clock. This class is a wrapper on top of rtc::TimestampAligner.
 */
public class TimestampAligner {
    /**
     * Wrapper around rtc::TimeNanos(). This is normally same as System.nanoTime(), but call this
     * function to be safe.
     */
    public static long getRtcTimeNanos() {
        return nativeRtcTimeNanos();
    }

    private volatile long nativeTimestampAligner = nativeCreateTimestampAligner();

    /**
     * Translates camera timestamps to the same timescale as is used by rtc::TimeNanos().
     * |cameraTimeNs| is assumed to be accurate, but with an unknown epoch and clock drift. Returns
     * the translated timestamp.
     */
    public long translateTimestamp(long cameraTimeNs) {
        checkNativeAlignerExists();
        return nativeTranslateTimestamp(nativeTimestampAligner, cameraTimeNs);
    }

    /**
     * Dispose native timestamp aligner.
     */
    public void dispose() {
        checkNativeAlignerExists();
        nativeReleaseTimestampAligner(nativeTimestampAligner);
        nativeTimestampAligner = 0;
    }

    private void checkNativeAlignerExists() {
        if (nativeTimestampAligner == 0) {
            throw new IllegalStateException("TimestampAligner has been disposed.");
        }
    }

    private static native long nativeRtcTimeNanos();

    private static native long nativeCreateTimestampAligner();

    private static native void nativeReleaseTimestampAligner(long timestampAligner);

    private static native long nativeTranslateTimestamp(long timestampAligner, long cameraTimeNs);
}
